Department of Psychology, University of Bonn Bonn, Germany ; Center for Economics and Neuroscience, University of Bonn Bonn, Germany.
Front Hum Neurosci. 2013 Jun 4;7:242. doi: 10.3389/fnhum.2013.00242. eCollection 2013.
One of the most prominent paradigms in neuroeconomics is the ultimatum game (UG) that provides a framework for the study of pro-social behavior in two players interacting anonymously with each other: Player 1 has to split an endowment with player 2. Player 2 can either accept or reject the offer from player 1. If player 2 accepts the offer then the money is split as proposed by player 1. In case of rejection both players get nothing. Until now only one twin study investigated the heritability of the behavior in the UG. Results indicated a strong heritability for the decision behavior of player 2 whereas no genetic influence on player 1 behavior could be detected. Further studies are mandatory to validate these heritability estimates. However, a first candidate polymorphism, the DRD4 exon III, constituting the biological basis of the heritability in the responder behavior has already been identified in a Chinese sample (Zhong et al., 2010). Until now genetic studies in Caucasians on the UG are lacking. The present study wants to fill this gap by investigating the UG in a healthy German sample. Moreover, we intend to find candidate genes that are associated with the first-mover-behavior. In a sample of N = 130 healthy participants an online version of the UG was conducted and polymorphisms of the dopamine D2 receptor gene (DRD2) and the DRD4 exon III VNTR were genotyped. We could confirm the DRD4 exon III effect on the responder behavior and the absence of an effect on the proposer behavior reported before. In line with Zhong et al. (2010) carriers of the 4/4 genotype showed a significant higher minimal acceptable offer (p = 0.023) than subjects with any other genotype. Furthermore, a DRD2-haplotype-block containing the single nucleotide polymorphisms rs1800497 and rs2283265 was significantly associated with the amount player1 offered (p = 0.005) but not with the decision of player 2. Results support the importance of the dopaminergic system for pro-social behavior.
神经经济学中最突出的范式之一是最后通牒博弈（UG），它为研究两个匿名相互作用的玩家之间的亲社会行为提供了一个框架：玩家 1 必须与玩家 2 分配一笔奖金。玩家 2 可以接受或拒绝玩家 1 的提议。如果玩家 2 接受提议，那么钱就按照玩家 1 的提议分配。如果拒绝，那么双方都没有得到任何东西。到目前为止，只有一项双胞胎研究调查了 UG 行为的遗传性。结果表明，玩家 2 的决策行为具有很强的遗传性，而玩家 1 的行为则没有遗传影响。需要进一步的研究来验证这些遗传估计。然而，已经在一个中国样本中确定了第一个候选多态性，即 DRD4 外显子 III，它构成了响应者行为遗传的生物学基础（Zhong 等人，2010）。到目前为止，在白种人中的 UG 遗传研究还缺乏。本研究旨在通过对德国健康样本进行 UG 研究来填补这一空白。此外，我们还打算寻找与先发制人行为相关的候选基因。在一个 N = 130 名健康参与者的样本中，进行了 UG 的在线版本，并且对多巴胺 D2 受体基因（DRD2）和 DRD4 外显子 III VNTR 的多态性进行了基因分型。我们可以确认 DRD4 外显子 III 对响应者行为的影响，以及之前报道的对提议者行为没有影响。与 Zhong 等人（2010）的研究结果一致，4/4 基因型的携带者表现出明显更高的最小可接受报价（p = 0.023），而任何其他基因型的受试者则没有。此外，含有单核苷酸多态性 rs1800497 和 rs2283265 的 DRD2 单倍型块与玩家 1 提供的金额显著相关（p = 0.005），但与玩家 2 的决策无关。结果支持多巴胺能系统对亲社会行为的重要性。
